Method and apparatus for objective assessment of in-ear device acoustical performance

ABSTRACT

A method and apparatus for objectively assessing acoustical performance of an in-ear device having a passageway extending there through use a dual microphone probe that removably engages the passageway. The acoustical performance of the in-ear device is performed with the in-ear device inserted into the ear canal of the user and a reference sound source. A clip holding the probe in an acoustic near field of the sound source permits real time calibration thereof. The method and apparatus allow on-site and in-situ measurement of a predicted personal attenuation rating of the device, a subject-fit re-insertion test, an acoustic seal test, a rating test, a stability and reliability test, as well as a protection test of the device with an assessment of a filtered predicted exposure level at the ear for a specific noise exposure level. The apparatus may be simply housed along with the sound source for in-field evaluation tests.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation of U.S. patentapplication Ser. No. 16/797,228, filed on Feb. 21, 2020, which is acontinuation of U.S. Pat. No. 10,645,505, which is a divisional of U.S.Pat. No. 9,167,365, which is a divisional of U.S. Pat. No. 8,254,587,which is a divisional of U.S. Pat. No. 8,254,586, which is a divisionalof U.S. Pat. No. 7,688,983, and claims priority to U.S. ProvisionalPatent Application No. 60/526,968, filed on Dec. 5, 2003.

FIELD OF THE INVENTION

The present invention relates to in-ear devices and is more particularlyconcerned with a method and apparatus for objective assessment of in-eardevice acoustical performance.

BACKGROUND OF THE INVENTION

The noisy environment in our industrial society is a health hazard tonumerous workers as well as to people engaged in recreational activitiesgenerating loud noises.

Users often wear earplugs when operating light machinery such aschainsaws or heavy machinery such as paper industry, printing industry,aircraft industry machines, when participating in sporting activitiessuch as shooting, and when attending various spectator events such asautomobile races, truck pulls, and rock concerts, and the like.

The art generally refers to different types of earplugs such as“universal fit” type earplugs that are intended to adapt to the contoursof any person's ear canal to provide hearing protection; custom-moldedearplugs that have advantages in their comfort, more reliable fit andlower long-term costs due to longer usable life; and semi-custom-moldedexpandable earplugs that are pre-shaped earplugs having the approximateshape of the ear canal of the individual and expanded with a settablecompound material injected therein.

All the above specifically refer to earplugs but it is to be understoodthat it is similarly applicable to any in-ear device, the latterreferring to either earplug device (or hearing protection device (HPD))or hearing aid device (HAD) for which an attenuation level or anamplification performance level is seek respectively.

One important aspect of preventing hearing loss is the accuratedetermination of protection from noise offered by an HPD. Protectionmust be sufficient to protect hearing from noise damage, but should notover-attenuate and interfere with communication and warning signaldetection.

Current HPD evaluation is done by using a variety of technicalevaluations, statistical corrections and estimations.

Real-Ear Attenuation at Threshold (REAT) is a subjective method ofdetermining the attenuation of a hearing protection device bysubtracting the open-ear (unprotected) threshold of hearing from theoccluded ear threshold (with the hearing protector in place).

The method for determining REAT is similar to the standard hearing test.The subject is tested in the following manner. Specific tones are givenand subject responds when the tones are heard. The hearing threshold isdetermined based on a given number of positive responses at given soundlevels. The REAT will therefore represent the value of attenuation ofthe HPD reported by the tested individual.

Noise Reduction Rating (NRR) is an estimate of hearing protectioncapability determined by applying a statistical analysis to a series ofREAT measurements. It is a single value figure that estimates theminimum noise reduction measurement theoretically obtained by 98% of theindividuals in a laboratory setting.

This percentile of 98% is obtained by subtracting, for every octaveband, twice the standard deviation from the mean attenuationmeasurements reported during the REAT test done according to ANSI 53.19.This is what the American National Standard requires for NRR calculationby the US Environmental Protection Agency (EPA).

The Personal Attenuation Rating (PAR) is a single number value thatrepresents the individual attenuation that each laboratory subjectobtained in the REAT test: it is indeed equivalent to a “personal NRR”.For example, the thirty PAR values obtained during an ANSI 53.19 test onan expandable type in-ear device as disclosed in U.S. Pat. No. 6,687,377to Voix et al. granted on Feb. 3, 2004 were recorded.

For this certification test, PAR values range from 18 dB (obtained inone trial) to 34 dB (obtained in two trials). The NRR calculated fromthis test series, due to the subtraction of two standard deviations, is15 dB. This is consistent with the very conservative NRR approach ofestimating protection for 98% of users, but is virtually useless indetermining individual protected values.

Additionally, there is no objective way of measuring an insertion loss(IL) value provided by an in-ear device. The IL estimation described inall standards (ANSI, ISO, CSA, etc.) is subjectively determined by theindividual wearing the in-ear device, as better described hereinbelow.

All standards, such as ANSI, ISO, CSA and the like, require an insertionloss (IL) subjective estimation, generally expressed in dB (decibels),of the acoustic seal provided by the in-ear device based on a ratio ofREAT values determined at the tympanic membrane, or eardrum, by theindividual himself (thereby subjective), with and without the in-eardevice.

Examples of assessments of acoustical performance of in-ear devices arefound in the following documents:

-   -   U.S. Pat. No. 5,970,795 granted to Seidmann et al. on Oct. 26,        1999 for “Apparatus and method for testing attenuation of in-use        insert hearing protectors”;    -   U.S. Pat. No. 5,757,930 granted to Seidmann et al. on May 26,        1998 for “Apparatus and method for testing attenuation of in-use        insert hearing protectors”;    -   U.S. Pat. No. 5,577,511 granted to Killion on Nov. 26, 1996 for        “Occlusion meter and associated method for measuring the        occlusion of an occluding object in the ear canal of a subject”;    -   U.S. Pat. No. 5,317,273 granted to Hanson et al. on May 31, 1994        for “Hearing protection device evaluation apparatus”; and    -   U.S. Pat. No. 4,060,701 granted to Epley on Nov. 29, 1977 for        “Method for testing acoustical attenuation of hearing        protectors”.    -   The last method taught by Epley is another subjective evaluation        method and suffers from the same weaknesses as all the other        subjective methods, naming:    -   the subjectivity of the measurements is a great source of        uncertainty and also significantly reduces the possibility of        repeatability of the measurements.    -   the subjective estimation of the attenuation is always larger        than the objective measurement of the corresponding IL,        especially in the low-frequencies; the “Occlusion Effect” tends        to increase the physiological noise (PN) present behind the        protector by modifying the acoustic radiation impedance seen        from the tympanic membrane.

Other ways of measuring acoustical attenuation or acoustic seal of anin-ear device disclose some devices that could measure the pneumaticpressure leakage of an in ear-device to later on predict its acousticalattenuation or the presence of an “acoustic seal”. Obviously, this merestatic pressure drop measurement is insufficient to reliably predict theacoustic pressure drop, and numerous materials may prove to provideexcellent pressure seal and still perfectly have sound pressuretransmitted there through. For example, a ping-pong shell molded in theear could be tightly sealed therein, but will always transmit soundthere through.

Accordingly, there is a need for an apparatus and method for objectiveassessment of in-ear device acoustical performance.

SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide amethod and apparatus for objective assessment of in-ear deviceacoustical performance that obviate the above-mentioned disadvantages.

Key aspects and advantages of the present method and apparatus forobjective assessment of in-ear device acoustical performance:

-   -   It is personal: it indicates how well the in-ear device works        for the individual under test, in real in-field environment        conditions (as opposed to laboratory conditions).    -   It is objective: it does not require the cooperation of the        individual under test, neither it is susceptible to the        objectivity of this individual.    -   Understanding the performance parameters of the in-ear device        for the individual permits attenuation adjustments to match the        capabilities of the in-ear device to the actual noise        environment of the user to customize the device to the        individual for his activity noise environment with proper sound        filters and obtain a Filtered Predicted Exposure Level (F-PEL).    -   The corresponding software permits real-time in-situ assessment        of a Predicted Personal Attenuation Rating (P-PAR) on the field.    -   Assessment can include evaluation of the in-ear device in the        noise environment of the user either on the field or via audio        reproduction thereof. This can be very important where        particular octave bands dominate over the noise environment and        assessment of the effectiveness of the in-ear device in those        octave bands is of interest.    -   The process integrates with subject-fit protocols. The test is        repeatable, permitting evaluation of the performance of the        in-ear device at any time. This can be useful in working with        individuals to encourage and ensure proper usage and fitting of        the protector, by using either a complex (personal computer-type        or the like) or a simple (pocket-type or the like) apparatus.    -   Objective in-situ assessment of an acoustic seal of the in-ear        device under subject-fit condition, of a rating level of the        in-ear device considering the applicable standard and the actual        type of the device, of a protection level of the in-ear device        considering the applicable standard and the actual noise        environment the user is subjected to, and of a simple        reliability (stability) check of all tests performed on the        in-ear device by assuring the coherence of all measurements.

In accordance with an aspect of the present invention, there is provideda method for assessing in-situ an acoustic seal of an in-ear deviceusing an apparatus having a sound measurement device connected thereto,the in-ear device having a passageway extending therethrough, thepassageway being in fluid communication with an ear canal of an ear whenthe in-ear device is inserted therein, the sound measurement devicebeing removably engageable into the passageway, said method comprises:a) calibrating said sound measurement device by measuring a referencesound level with said sound measurement device when being submitted to areference sound source and when being located in a close relationshiprelative thereto; b) measuring a first sound level outside the ear canalwith said sound measurement device when submitted to the sound sourceand when located in a close relationship relative to the in-ear deviceand outside the ear canal; c) measuring a second sound level inside theear canal with said sound measurement device when submitted to the soundsource and when engaged into and occluding the passageway with thein-ear device inserted inside the ear canal; and d) assessing theacoustic seal of the in-ear device by subtracting said second soundlevel from said first sound level.

In one embodiment, step a) includes measuring a reference sound levelwith said sound measurement device when being submitted to a referencesound source and when being in an acoustic near field relative thereto.

In one embodiment, the method further includes: a1) assessing validityof said reference sound level by determining that said reference soundlevel is within a predetermined sound level amplitude range, if not stepa) is repeated.

Typically, step d) includes indicating presence of acoustic seal whenattenuation between said first and second sound levels is equal to orlarger than a predetermined threshold value within a predeterminedfrequency range.

In one embodiment, steps b) and c) are simultaneously performed usingfirst and second sound measurement devices, respectively.

Typically, step d) includes: d1) assessing validity of said first andsecond sound levels by determining coherence between said first andsecond sound levels, if not steps b) and c) are repeated.

Typically, step d1) includes determining coherence between said firstand second sound levels within a predetermined frequency range.Preferably, determining coherence between said first and second soundlevels includes determining that said second sound level substantiallylinearly follows a contour of said first sound level.

Typically, step d) includes indicating presence of acoustic seal whenattenuation between said first and second sound levels is equal to orlarger than a predetermined threshold value within a predeterminedfrequency range.

In one embodiment, step d) includes assessing the acoustic seal of thein-ear device by subtracting said second sound level from said firstsound level and using a compensation term relating to the in-ear device.

In one embodiment, step a) includes calibrating first and second soundmeasurement devices by measuring first and second reference sound levelswith said first and second sound measurement devices, respectively, whenbeing submitted to a reference sound source and when being located in aclose relationship relative thereto; and wherein steps b) and c) aresimultaneously performed using said first and second sound measurementdevices, respectively.

Typically, step a) includes simultaneously measuring first and secondreference sound levels with said first and second sound measurementdevices, respectively, when being submitted to a reference sound sourceand when being in an acoustic near field relative thereto.

Typically, the method further includes: a1) assessing validity of saidfirst and second reference sound levels by determining that said firstand second reference sound levels are within a predetermined sound leveltemplate range, if not step a) is repeated.

Typically, step a) includes simultaneously measuring first and secondreference sound levels with said first and second sound measurementdevices, respectively, when being submitted to a reference sound sourceand when being in an acoustic near field relative thereto, anddetermining a transfer function between said first and second referencesound levels.

In one embodiment, the method further includes: a1) assessing validityof said first and second reference sound levels by determining that saidtransfer function is within a predetermined sound level template range,if not step a) is repeated.

Typically, step d) includes assessing the acoustic seal of the in-eardevice by subtracting said second sound level from said first soundlevel and using said transfer function and a compensation term relatingto the in-ear device.

In accordance with another aspect of the present invention, there isprovided an apparatus for assessing in-situ an acoustic seal of anin-ear device, the in-ear device having a passageway extendingtherethrough, the passageway being in fluid communication with an earcanal of an ear when the in-ear device is inserted therein, saidapparatus comprises: a controller unit operatively connectable to asound source; a sound measurement device operatively connecting to saidcontroller unit, said sound measurement device being selectivelylocatable in a close relationship relative to the in-ear device andoutside the ear canal for measuring a first sound level outside the earcanal when submitted to the sound source, said sound measurement devicebeing removably engageable into the passageway to selectively occludethe passageway for measuring a second sound level inside the ear canalwith the in-ear device inserted therein when submitted to the soundsource; and a means for releasably supporting said sound measurementdevice located in a close relationship relative to the sound source formeasuring a reference sound level when being submitted thereto.

In one embodiment, the means for supporting said sound measurementdevice is a supporting device, preferably a resilient clip, mountable onthe sound source, said clip releasably and resiliently holding saidsound measurement device.

In one embodiment, the controller unit controls operation of the soundsource.

In one embodiment, the controller unit includes the sound source.

In one embodiment, the sound measurement device is a first soundmeasurement device, said apparatus further including a second soundmeasurement device operatively connecting to said controller device,said first sound measurement device being selectively locatable in aclose relationship relative to the in-ear device and outside the earcanal for measuring the first sound level outside the ear canal whensubmitted to the sound source, said second sound measurement devicebeing removably engageable into the passageway to selectively occludethe passageway for measuring the second sound level inside the ear canalwith the in-ear device inserted therein when submitted to-the soundsource. And, the means for releasably supporting said sound measurementdevice releasably supports said first and second sound measurementdevices located in a close relationship relative to the sound source formeasuring first and second reference sound levels when being submittedthereto, relatively.

Typically, the first and second sound measurement devices are connectedto one another, preferably in a back-to-back relationship relative toone another to form a dual microphone probe.

In one embodiment, the apparatus further includes a user interface unitoperatively connecting to said controller unit.

Typically, the controller unit analyzes said first and second referencesound levels and assesses calibration of said first and second soundmeasurement devices, said controller unit communicating with said userinterface unit to indicate to the user proper functioning of said firstand second sound measurement devices.

Typically, the controller unit analyzes said first and second soundlevels and assesses validity of said first and second sound levels, saidcontroller unit communicating with said user interface unit to indicateto the user proper measurements of said first and second sound levels.

Typically, the controller unit further assesses an acoustic seal of thein-ear device by comparing said first and second sound levels to oneanother and by using a transfer function determined from said first andsecond reference sound levels, said controller unit communicating withsaid user interface unit to indicate to the user proper acoustic seal ofthe in-ear device inside the ear.

Typically, the controller unit further assesses an acoustic seal byfurther using a compensation term relating to the in-ear device.

In one embodiment, the controller unit assesses an acoustic seal of thein-ear device by comparing said first and second sound levels to oneanother, said controller unit further assessing an acoustic seal byfurther using a compensation term relating to the in-ear device, saidcontroller unit communicating with said user interface unit to indicateto the user proper acoustic seal of the in-ear device inside the ear.

In one embodiment, the user interface unit includes at least one of akeypad, a keyboard, an alpha-numerical display, a speaker, a led-typedisplay, a monitor-type display, a socket-type connection port and awireless-type connection port.

In accordance with another aspect of the present invention, there isprovided a method for assessing an acoustical performance of an in-eardevice using an apparatus having a sound measurement device connectedthereto, the in-ear device having a passageway extending therethroughfor receiving an acoustic damper therein, the acoustic damper having apredetermined acoustic attenuation thereof, the passageway being influid communication with an ear canal of an ear when the in-ear deviceis inserted therein, the sound measurement device being removablyengageable into the passageway, said method comprises: a) calculating anacoustical performance of the in-ear device with the acoustical damperinserted in the passageway thereof from a measured blocked acousticattenuation obtained with the passageway being occluded using a soundmeasurement device selectively engaged therein and the predetermineddamper acoustic attenuation.

In one embodiment, the method further includes, before step a), the stepof: measuring a blocked acoustic attenuation of the in-ear device withthe passageway being occluded using the sound measurement deviceselectively and alternately engaged therein and disengaged therefrom.

In one embodiment, the in-ear device is for being worn by a usersubjected to an environment with a predetermined noise exposure level,said method further includes: b) calculating a filtered exposure levelat an ear of the user would be subjected to when protected by the in-eardevice with the acoustic damper inserted in the passageway thereofinside the environment from the calculated acoustical performance andthe predetermined sound exposure level.

In one embodiment, the passageway is for receiving one of a plurality ofacoustic dampers, each one of the plurality of acoustic dampers having arespective predetermined damper acoustic attenuation thereof, saidmethod includes: a) calculating a respective acoustical performance ofthe in-ear device with each one of the plurality of acoustic dampersinserted in the passageway thereof from a measured blocked acousticattenuation obtained with the passageway being occluded using a soundmeasurement device selectively engaged therein and a corresponding saidpredetermined damper acoustic attenuations; b) calculating a respectivefiltered exposure level at an ear of the user would be subjected to whenprotected by the in-ear device with respective said plurality of theacoustic dampers inserted in the passageway thereof inside theenvironment from respective said calculated acoustical performances andthe predetermined sound exposure level.

Typically, the method further includes: c) selecting one of theplurality of acoustic dampers providing a corresponding filteredexposure level within or closest to a predetermined optimal exposurelevel range.

In one embodiment, the method further includes, before step a), forobtaining said predetermined damper acoustic attenuation, the steps of:submitting a user wearing the in-ear device with the passageway thereofbeing occluded to a gradually increasing or decreasing a volume of asound level of a predetermined frequency range to determine a firstsound level threshold value at which the user start or stop hearing thesound; submitting a user wearing the in-ear device with the acousticdamper inserted in the passageway thereof to a gradually increasing ordecreasing a volume of a sound level of a predetermined frequency rangeto determine a second sound level threshold value at which the userstart or stop hearing the sound; and calculating the predetermineddamper acoustic attenuation from a difference between said first andsecond sound level threshold values.

Typically, calculating the predetermined damper acoustic attenuationincludes calculating the predetermined damper acoustic attenuation froma difference between first and second average sound level thresholdsobtained from a statistically significant number of said first andsecond sound level threshold values, respectively.

In one embodiment, the method further includes, before step a), forobtaining said, predetermined damper acoustic attenuation, the steps of:submitting a user wearing the in-ear device with the passageway thereofbeing occluded to a gradually increasing or decreasing a frequency of asound level of a predetermined volume range to determine a first soundlevel threshold value at which the user stop or start hearing the sound;submitting a user wearing the in-ear device with the acoustic damperinserted in the passageway thereof to a gradually increasing ordecreasing a frequency of a sound level of a predetermined volume rangeto determine a second sound level threshold value at which the user stopor start hearing the sound; and calculating the predetermined damperacoustic attenuation from a difference between said first and secondsound level threshold values.

Typically, calculating the predetermined damper acoustic attenuationincludes calculating the predetermined damper acoustic attenuation froma difference between first and second average sound level thresholdsobtained from a statistically significant number of said first andsecond sound level threshold values, respectively.

In accordance with another aspect of the present invention, there isprovided an apparatus for assessing an acoustical performance of anin-ear device, the in-ear device having a passageway extendingtherethrough for receiving an acoustic damper therein, the acousticdamper having a predetermined acoustic attenuation thereof, thepassageway being in fluid communication with an ear canal of an ear whenthe in-ear device is inserted therein, said apparatus comprises: acontroller unit operatively connectable to a sound source; a userinterface unit operatively connecting to said controller unit to allow auser to interface therewith by storing the predetermined acousticattenuation of the acoustic damper therein; and a sound measurementdevice operatively connecting to said controller unit, said soundmeasurement device being selectively locatable in a close relationshiprelative to the in-ear device and outside the ear canal for measuring afirst sound level outside the ear canal when submitted to the soundsource, said sound measurement device being removably engageable intothe passageway to selectively occlude the passageway for measuring asecond sound level inside the ear canal with the in-ear device insertedtherein when submitted to the sound source; said controller unitcalculating an acoustical performance of the in-ear device with theacoustical damper inserted in the passageway thereof from a blockedacoustic attenuation obtained with said first and second sound levelsand the predetermined damper acoustic attenuation.

In one embodiment, the in-ear device is for being worn by a usersubjected to an environment with a predetermined noise exposure levelstorable within said controller unit, said controller unit calculating afiltered exposure level an ear of the user would be subjected to whenprotected by the in-ear device with the acoustic damper inserted in thepassageway thereof inside the environment from the calculated acousticalperformance and the predetermined sound exposure level.

In one embodiment, the passageway is for receiving one of a plurality ofacoustic dampers, each one of the plurality of acoustic dampers having arespective predetermined damper acoustic attenuation thereof storablewithin said controller unit, said controller unit calculating arespective acoustical performance of the in-ear device with each one ofthe plurality of acoustic dampers inserted in the passageway thereoffrom a measured blocked acoustic attenuation obtained with thepassageway being occluded using a sound measurement device selectivelyengaged therein and a corresponding said predetermined damper acousticattenuations, said controller unit further calculating a respectivefiltered exposure level an ear of the user would be subjected to whenprotected by the in-ear device with respective said plurality of theacoustic dampers inserted in the passageway thereof inside theenvironment from respective said calculated acoustical performances andthe predetermined sound exposure level.

Typically, the controller unit further selects one of the plurality ofacoustic dampers providing a corresponding filtered exposure levelwithin or closest to a predetermined optimal protection level rangestorable therein.

In accordance with another aspect of the present invention, there isprovided a method for assessing an acoustical performance of an in-eardevice using an apparatus having a sound measurement device connectedthereto, the in-ear device having a passageway extending therethrough,the passageway being in fluid communication with an ear canal of an earwhen the in-ear device is inserted therein, the sound measurement devicebeing removably engageable into the passageway, said method comprises:a) measuring a first sound level outside the ear canal with said soundmeasurement device when submitted to the sound source and when locatedin a close relationship relative to the in-ear device and outside theear canal; b) measuring a second sound level inside the ear canal withsaid sound measurement device when submitted to the sound source andwhen engaged into and occluding the passageway with the in-ear deviceinserted inside the ear canal after being fitted thereto and beforeremoval therefrom; c) measuring a third sound level inside the ear canalwith said sound measurement device when submitted to the sound sourceand when engaged into and occluding the passageway with the in-eardevice inserted inside the ear canal after removal therefrom andreinsertion therein by the wearer thereof; d) assessing a referenceacoustic seal of the in-ear device by subtracting said second soundlevel from said first sound level and an actual acoustic seal of thein-ear device by subtracting said third sound level from said firstsound level; and e) assessing a rating of the in-ear device by comparingsaid actual acoustic seal relative to said reference acoustic seal.

Typically, steps a) and b) are simultaneously performed using first andsecond sound measurement devices, respectively.

Typically, step e) further includes comparing said obtained rating to astandardized rating value corresponding to a type of the in-ear device.

In one embodiment, step c) includes measuring a third sound level insidethe ear canal with said sound measurement device when submitted to thesound source and when engaged into and occluding the passageway with thein-ear device inserted inside the ear canal after removal therefrom andreinsertion therein by the wearer thereof, and measuring a fourth soundlevel outside the ear canal with said measurement device when submittedto the sound source and when located in a close relationship relative tothe in-ear device and outside the ear canal; and wherein step d)includes assessing a reference acoustic seal of the in-ear device bysubtracting said second sound level from said first sound level and anactual acoustic seal of the in-ear device by subtracting said thirdsound level from said fourth sound level.

Typically, step b) includes: b1) assessing validity of said first andsecond sound levels by determining coherence between said first andsecond sound levels, if not steps a) and b) are repeated; and step c)includes: c1) assessing validity of said third and fourth sound levelsby determining coherence between said third and fourth sound levels, ifnot step c) is repeated.

Typically, steps b1) and c1) include determining coherence between saidfirst and second sound levels within a predetermined frequency range andbetween said third and fourth sound levels within said predeterminedfrequency range, respectively.

Typically, determining coherence between said first and second soundlevels includes determining that said second sound level substantiallylinearly follows a contour of said first sound level, and determiningcoherence between said third and fourth sound levels includesdetermining that said third sound level substantially linearly follows acontour of said fourth sound level.

Typically, the method further includes, before step a), the step of:simultaneously measuring first and second reference sound levels withsaid first and second sound measurement devices, respectively, whenbeing submitted to a reference sound source and when being in anacoustic near field relative thereto, and determining a transferfunction between said first and second reference sound levels.

In accordance with another aspect of the present invention, there isprovided an apparatus for assessing in-situ an acoustic seal of anin-ear device, the in-ear device having a passageway extendingtherethrough, the passageway being in fluid communication with an earcanal of an ear when the in-ear device is inserted therein, saidapparatus comprises: a controller unit operatively connectable to asound source; a user interface unit operatively connecting to saidcontroller unit to allow a user to interface therewith by storing thepredetermined acoustic attenuation of the acoustic damper therein; and asound measurement device operatively connecting to said controller unit,said sound measurement device being selectively locatable in a closerelationship relative to the in-ear device and outside the ear canal formeasuring a first sound level outside the ear canal when submitted tothe sound source, said sound measurement device being removablyengageable into the passageway to selectively occlude the passageway formeasuring, when submitted to the sound source, a second sound levelinside the ear canal with the in-ear device inserted therein beingfitted thereto and before removal therefrom, and a third sound levelinside the ear canal the in-ear device inserted inside the ear canalafter removal therefrom and reinsertion therein by the wearer thereof;said controller unit calculating a reference acoustic seal of the in-eardevice by subtracting said second sound level from said first soundlevel, an actual acoustic seal of the in-ear device by subtracting saidthird sound level from said first sound level, and a rating of thein-ear device by comparing said actual acoustic seal relative to saidreference acoustic seal.

Typically, the controller unit indicates presence of acceptable acousticseal when said actual acoustic seal is within a predetermined range fromsaid reference acoustic seal.

Typically, the controller unit compares said obtained rating to astandardized rating value corresponding to a type of the in-ear deviceand stored therein.

In one embodiment, the controller unit assesses validity of said firstand second sound levels by determining coherence between said first andsecond sound levels, if not said first and second sound levels are beingre-measured; and assesses validity of said third and fourth sound levelsby determining coherence between said third and fourth sound levels, ifnot said third and fourth sound levels are being re-measured.

Typically, the controller unit determines coherence between said firstand second sound levels within a predetermined frequency range andbetween said third and fourth sound levels within said predeterminedfrequency range, respectively.

Other objects and advantages of the present invention will becomeapparent from a careful reading of the detailed description providedherein, with appropriate reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Further aspects and advantages of the present invention will becomebetter understood with reference to the description in association withthe following Figures, in which similar references used in differentFigures denote similar components, wherein:

FIG. 1 is a simplified schematic diagram of an apparatus for assessingin-situ an acoustic seal of an in-ear device in accordance with anembodiment of the present invention;

FIGS. 2 and 3 are pictorial representations of the different locationsfor sound pressure level measurement inside an individual's ear canalwithout (unoccluded) and with (occluded) an in-ear device, respectively;

FIG. 4 is a simplified flow diagram of a method for assessing in-situ anacoustic seal of an in-ear device in accordance with an embodiment ofthe present invention;

FIG. 5 is a simplified flow diagram of an embodiment of a method forassessing an acoustical performance of an in-ear device according to thepresent invention;

FIG. 6 is a simplified schematic block diagram illustrating the methodof FIG. 5; and

FIG. 7 is a simplified flow diagram of another embodiment of a methodfor assessing an acoustical performance of an in-ear device according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the annexed drawings the preferred embodiments of thepresent invention will be herein described for indicative purpose and byno means as of limitation.

Referring now in more detail to FIG. 1, there is shown an apparatus 10for assessing in situ acoustical performance of an in-ear device 12 inaccordance with an embodiment of the present invention. The in-eardevice 12 or earplug, typically made out of generally soft materialssuch as silicones, acrylic materials and the like, is typically firstinserted inside the ear canal 14 of the ear 16 of an individual (user orwearer) and then fitted to the contour thereof using a thermo-settablecompound 18 (shown in dotted lines) injected inside the in-ear device12. The earplug 12 typically includes at least one passageway 20 orsound bore that extends there through to be in fluid communication withthe ear canal 14 when the earplug 12 is inserted therein. Although anearplug 12 is being shown throughout the Figures for illustrationpurposes, one skilled in the art would understand that any type ofin-ear device (HPDs, HADs or the like) could be used without departingfrom the scope of the present invention.

The apparatus 10 typically includes a controller unit 22 operativelyconnected to a broadband reference sound source 24 to control operationthereof. The sound source 24 provides a sound typically having afrequency range varying from about 100 Hz to about 10000 Hz such thatthe following preferred octave bands which enclose most audible sounds(including conversation frequency range of about 300 Hz to about 3000Hz) are essentially covered: 125 Hz, 250 Hz, 500 Hz, 1000 Hz, 2000 Hz,4000 Hz and 8000 Hz. Typically, the controller 22 is a personal-typecomputer, a laptop, a palm computer or the like that include a centralprocessing unit (not shown) or the like to process the data and performassessments. A dual microphone probe 26 that is removably engageableinto the passageway 20 of the earplug 12 operatively connects to thecontroller 22. The probe 26 typically includes first 28 and second 30sound measurement devices or microphones mounted in a back-to-backrelationship relative to one another such that the first microphone 28measures an external sound pressure level in proximity to the earplug 12and the second microphone 30 measures an internal sound pressure levelinside the ear canal 14 when the earplug 12 is inserted therein,respectively.

Although the used of a dual microphone probe 26 is preferred, one couldconsider using only one sound measurement device 28 to successivelyperform all required sound level measurements discussed hereinbelowwithout departing from the scope of the present invention.

A sound pressure level or sound level refers to a sound of anypredetermined frequency and/or amplitude ranges to cover anypredetermined amount of octave bands, depending on the application, testand/or apparatus.

A user interface unit 32 is operatively connected to the controller 22for the user to operate the apparatus 10, provide some inputs and datathereinto and get outputs or data therefrom. The user interface 32 arewell known and typically includes at least one of a keypad 34 a, akeyboard 34 b, an alpha-numerical display 34 c, a speaker 34 d, aled-type display 34 e, a monitor-type display 34 f, a socket-typeconnection port 34 g and a wireless-type (Infra-Red (IR), microwaves(MW), voice and the like) connection port 34 h and the like fordifferent types of communication protocols.

The controller 22 could also be housed within the same housing as thesound source 24 and interface knobs and led-type display 34 e, such thatthe apparatus 10 could be a “stand-alone” type for in-field assessmentof in-ear device acoustical performance.

The apparatus 10 typically includes a means 36 for releasably supportingthe probe 26 in a close relationship relative to the sound source 24 formeasurements of reference sound pressure levels and/or calibration ofthe apparatus 10 through proper functioning of the two microphones 28,30 when being submitted to a reference sound therefrom. The means forsupporting the probe 26 is a supporting device such as a resilient clip36 or the like mounted on the sound source 24, typically in the middleof the speaker grid 38 thereof. Accordingly, the clip 36 releasablysupports the probe 26 inside the acoustic near field generated by thesound source 24, as shown in dotted lines in FIG. 1.

As mentioned hereinabove, the Personal Attenuation Rating (PAR) is asingle number value that represents the individual attenuation that eachlaboratory subject obtained in the Real-Ear Attenuation at Threshold(REAT) test: it is indeed equivalent to a “personal Noise ReductionRating (NRR)”.

Determining true PAR for each individual would provide very usefulinformation to determine the hearing protector adequacy and sufficiency.Since it is impossible, even theoretically, to predict PAR from NRR,other objective means to determine PAR were scientifically developed.

The Noise Reduction (NR) is an objective method which is the soundpressure level (SPL) difference measured at the external part of thehearing protection device 12 (HPD) (by an external microphone 28)compared to the SPL measured inside the HPD (by an internal microphone30).

From an individual measurement of NR, it is possible to predict thecorresponding PAR using a “compensation function” which is applied tothe NR for every octave band. The “compensation function” addressestransfer function of the outer ear (TFOE), head and torso diffraction ofthe reference noise source, the length of the microphone probe, theimpedance of the occluded ear canal, the resonant frequency of the earcanal, and the like variables. Due to the fact that the compensationfunction is normally distributed, the predicted REAT will also follow anormalized “Bell Curve”.

P-PAR is a global value which confidently represents the PAR. This valueis therefore “personal” to the end-user and is extremely useful inassuring the adequate protection needed by this individual rather than astatistically derived value or popular estimate.

It is to be noted that the present invention allows for a real-timemonitoring of the inflation of an expandable in-ear device 12 beingfitted inside an ear 16 as described in U.S. Pat. No. 6,687,377 grantedto Voix et al. on Feb. 3, 2004, although not specifically required.

Also, the present invention is a field method to estimate the noiseattenuation obtained by such expandable earplug 12 as worn in theworkplace. The proposed method is a MIRE method (Microphone In the RealEar) that uses the Noise Reduction (NR) measurement on one's earplug topredict, based on a statistical approach, the corresponding subjectiveattenuation (ATT) that this user would report during a REAT (Real-EarAttenuation at Threshold) test.

The prediction of an in-ear device attenuation (as reported with REATmethod) from on an objective Noise Reduction measurement (MIRE) useseither:

-   -   a statistical approach: A statistical “compensation function” is        applied per octave band to estimate the REAT from the NR        measured.    -   a personal dedicated approach: An analytical “compensation        function” is computed from the exact physical and mechanical        properties of the subject ear canal as identified using the        identification method described hereinafter.

More specifically, and referring to FIGS. 2 and 3, it is known that theIL corresponding to the difference in sound pressure level at eardrum 40between unoccluded and occluded conditions can be determined by:

IL=NR+TFOE

where TFOE is the Transfer Function of the Outer Ear, for an unoccludedear 16 (FIG. 2), and is equal to:

${TFOE} = {20{\log_{10}\left( \frac{P_{3}}{P} \right)}}$

In an occluded ear 12 (FIG. 3), the NR is determined by:

${NR} = {20{\log_{10}\left( \frac{P}{P_{3}^{\prime}} \right)}}$

It has been clearly demonstrated that the attenuation reported during aREAT measurement may be slightly overestimated (below 500 Hz) due to themasking effect of the physiological noise (PN) on occluded thresholds.It remains that this reported attenuation is a subjective evaluation ofthe IL and, practically:

REAT=IL+PN

The measured noise reduction (NR_(M)) measured typically using a dualmicrophone probe 26 adjacent the in-ear device 12 and measuring thesound pressure levels outside the device 12 being worn by the user andinside the ear canal 14 via the passageway 20 (or sound bore) of thedevice (see FIG. 1), respectively, is:

${NR}_{M} = {20{\log_{10}\left( \frac{P_{0}^{\prime}}{P_{2}^{''}} \right)}}$

Therefore, combining the previous equations, the measured noisereduction NR_(M) can be linked to the reported attenuation as follows:

${REAT} = {{NR}_{M} + \underset{\underset{COMP}{︸}}{{TFOE} + {20{\log_{10}\left( \frac{P_{2}^{''}}{P_{2}^{\prime}} \right)}} + {20{\log_{10}\left( \frac{P_{2}^{\prime}}{P_{3}^{\prime}} \right)}} + {20{\log_{10}\left( \frac{P}{P_{0}^{\prime}} \right)}} + {PN}}}$

where:

-   -   (P″₂/P′₂) stands for the “tube effect” of the microphone probe        26;    -   (P′₂/P′₃) stands for another “tube effect” of the residual ear        canal portion;    -   (P/P′₀) stands for the diffraction effect of the subject's head        and torso.    -   A compensation term COMP that contains all the above three        corrections, the TFOE and the PN masking effect can be defined.        This compensation COMP is subject sensitive and, for a large        group, distributes as a standard or normal distribution.        Therefore, the simultaneous recording of the NR_(M) and the REAT        for a large number of subjects will determine a global        compensation COMP and a corresponding compensation per octave        band COMP′ (as identified by the indicia ‘I’), respectively.        Obviously, the same rationale could be considered by using third        of octave bands, twelfth of octave bands or the like without        departing from the scope of the present invention.

Knowing the octave band based compensation term COMP′, a correspondingREAT′ can be obtained. Further knowing that the NRR (slightly modifiedto correspond to selected octave bands) is obtained by:

${NRR} = {{10\log_{10}{\sum\limits_{i}10^{\frac{{100} + C_{i}}{10}}}} - {10\log_{10}{\sum\limits_{i}10^{\frac{{100} + A^{i} - \overset{\_}{{REAT}^{i}} + {2\sigma_{REAT}^{i}}}{10}}}} - 3}$

where REAT^(i) is a statistical average of REAT′;

-   -   C^(i) and A^(i) are octave band weighting factors, and    -   2σ^(i) _(REAT) is the two-standard deviation factor showing that        a 98% confidence level is considered.

Then the PAR can be derived as follows:

${PAR} = {{10\log_{10}{\sum\limits_{i}10^{\frac{{100} + C_{i}}{10}}}} - {10\log_{10}{\sum{10^{\frac{{100} + A^{i} - {{REA}T^{i}}}{10}}}}}}$

Also, the computation of a single number for the rating of a P-PAR usingthe in-ear device 12, or global personal attenuation rating, isstatistically derived from the normalized (

) averaged compensation term COMP^(i) and individual noise reductionNR_(ind) ^(i) as being:

P−PAR=PAR≡NR_(ind) ^(i)+

(COMP^(i) ,σ_(COMP) ^(i))

to give:

${P - {PAR}} = {\overset{\_}{\overset{\_}{PAR}} = {{10\log_{10}{\sum\limits_{i}10^{\frac{100 + C_{i}}{10}}}} - {10\log_{10}{\sum\limits_{i}10^{\frac{100 + A^{i} - \overset{\_}{{REAT}^{i}}}{10}}}}}}$

This permits the identification of physical and mechanical properties ofone's ear canal from an acoustical measurement.

More specifically, the present invention teaches a method for assessingin-situ an acoustic seal of an in-ear device 12 using an apparatus 10having a sound measurement device 28 connected thereto, as shown in thesimplified flow diagram of FIG. 4 in which all steps, including optionalones, are illustrated. The method comprises:

-   -   a) calibrating the sound measurement device 28 by measuring a        reference sound level with the sound measurement device 28 when        being submitted to a sound source 24 and when being located in a        close relationship relative thereto;    -   b) measuring a first sound level outside the ear canal 14 with        the sound measurement device 28 when submitted to the sound        source 24 and when located in a close relationship relative to        the in-ear device 12 and outside the ear canal 14;    -   c) measuring a second sound level inside the ear canal 14 with        the sound measurement device 28 when submitted to the sound        source 24 and when engaged into and occluding the passageway 20        with the in-ear device 12 inserted inside the ear canal 14; and    -   d) assessing the acoustic seal of the in-ear device 12 by        subtracting said second sound level from said first sound level.

The method further includes:

-   -   a1) assessing validity of said reference sound level by        determining that the reference sound level is within a        predetermined sound level amplitude range, if not step a) is        repeated.

Typically, steps b) and c) are simultaneously performed using first 28and second 30 sound measurement devices, respectively, preferably usingthe dual microphone probe 26 or the like. Accordingly, step a) includescalibrating first and second sound measurement devices by measuringfirst and second reference sound levels with the dual probe 26 whenbeing submitted to a reference sound source and when being located in aclose relationship or in an acoustic near field relative thereto. Stepa) further includes determining a transfer function between the firstand second reference sound levels.

Then, step a1) further includes assessing validity of the first andsecond reference sound levels by determining that the transfer functionis within a predetermined sound level template range.

Step d) further includes indicating presence of acoustic seal whenattenuation between the first and second sound levels is equal to orlarger than a predetermined threshold value within a predeterminedfrequency range. As an example, the predetermined threshold value couldbe 11 dB (the NR, ANSI 53.19 test, within the 98% percentile) at about250 Hz.

Typically, steps b) and c) are also simultaneously performed using first28 and second 30 sound measurement devices, respectively. And step d)includes:

-   -   d1) assessing validity of the first and second sound levels by        determining coherence there between preferably within a        predetermined frequency range, if not steps b) and c) are        repeated.

Determining coherence between the first 42 and second 44 sound levelsincludes determining that the second sound level 44 substantiallylinearly follows a contour of the first sound level 42, as schematicallydepicted in FIG. 1. For example, if the user happens to talk, cough oreven swallow during the measurement of the second sound level 44, thelatter would show acoustic noise induced by the user's voice, therebynot linearly following the contour of the first sound level 42, leadingto a non-coherence between the two.

Furthermore, step d) includes assessing the acoustic seal of the in-eardevice 12 by subtracting the second sound level 44 from said first soundlevel 42 and using the transfer function.

As described hereinabove, the assessment of the acoustic seal of thein-ear device 12 further includes using a compensation term (COMP) thatrelates to the type of in-ear device 12.

The calibration is typically performed before each test to ensure properfunctioning of the dual probe 26 as well as the real-time reassessmentof the transfer function thereof for accurate measurements.

The above detailed acoustic seal test ensures that the in-ear device 12or earplug fits properly inside the ear canal 14 of the user, therebyproviding a good acoustic seal.

A stability and reliability test that simply monitors the coherence ofthe transfer function (between external 28 and internal 30 microphones)in the 125 Hz octave band for example is easily performed by theapparatus 10 using the above method.

A similar method for assessing an acoustical performance of an in-eardevice 12 using an apparatus 10 is shown in the simplified flow diagramof FIG. 5 in which all steps, including optional ones, are illustrated.The passageway 20 of the in-ear device 12 is typically adapted toreceive an acoustic damper 46 therein, preferably inside a predeterminedsection or chamber 47 thereof having an enlarged diameter or the like.The acoustic damper 46 typically has a predetermined acousticattenuation thereof. The method comprises:

-   -   a) calculating an acoustical performance of the in-ear device 12        with the acoustical damper 46 inserted in the passageway 20        thereof from a measured blocked acoustic attenuation obtained        with the passageway 20 being occluded using a sound measurement        device 30 selectively engaged therein and the predetermined        damper acoustic attenuation.

Typically, the method further includes, before step a), the step of:

-   -   measuring a blocked acoustic attenuation of the in-ear device 12        with the passageway 20 being occluded using the sound        measurement device 30 being selectively and alternately engaged        therein and disengaged therefrom (or using a second sound        measurement device 28 in the environment).

The predetermined damper acoustic attenuation is typically obtainedthrough the following steps:

-   -   submitting a user wearing the in-ear device 12 with the        passageway 20 thereof being occluded to a gradually increasing        or decreasing a volume of a sound level of a predetermined        frequency range to determine a first sound level threshold value        at which the user start or stop hearing the sound;    -   submitting a user wearing the in-ear device 12 with the acoustic        damper 46 inserted in the passageway 20 thereof to a gradually        increasing or decreasing a volume of a sound level of a        predetermined frequency range to determine a second sound level        threshold value at which the user start or stop hearing the        sound; and    -   calculating the predetermined damper acoustic attenuation from a        difference between the first and second sound level threshold        values or preferably, from a difference between first and second        average sound level thresholds obtained from a statistically        significant number of the first and second sound level threshold        values, respectively.

Alternatively, the predetermined damper acoustic attenuation may betypically obtained through the same steps with reference to first andsecond sound threshold values determined with a gradually increasing ordecreasing a frequency of a sound level of a predetermined volume rangeat which the user stop or start hearing the sound.

As the in-ear device 12 is typically for being worn by a user subjectedto an environment with a predetermined noise exposure level, the methodfurther includes:

-   -   b) calculating a filtered exposure level at an ear of the user        would be subjected to when protected by the in-ear device 12        with the acoustic damper 46 inserted in the passageway 20        thereof inside the environment from the calculated acoustical        performance and the predetermined sound exposure level.

Since a plurality of acoustic dampers 48, each having a respectivepredetermined damper acoustic attenuation thereof, may be considered,the method would, after calculating respective filtered exposure levelswith the different dampers 48, further includes:

-   -   c) selecting one of the plurality of acoustic dampers 48        providing a corresponding filtered exposure level within or        closest to a predetermined optimal exposure level range,        typically between about 75 dBA and about 80 dBA.

Similarly, an exposure level range between about 70 dBA and about 75 dBAor between about 80 dBA and about 85 dBA would be considered acceptable.An exposure level above 85 dBA would be considered unacceptablyinsufficient and dangerous to the user for over exposure, while anexposure level below 70 dBA would be unacceptably overprotecting andalso dangerous because speech and warning signals would essentially notbe heard by the user.

To be more practical, similarly to the quasi-subjective evaluation ofthe REAT made to get the compensation term COMP and the PAR, anevaluation of the attenuation of an in-ear device in a full-blockconfiguration (ATT_(Full-block)) with the passageway occluded with aplug 50 or the like and in a filtered or “combo” configuration(ATT_(Combo)) with predetermined acoustic dampers 48, such as plasticpieces of different densities or the like, occluding the passageway canbe made to statistically assess the difference between the twoconfigurations and therefore get the attenuation of the damper asfollows:

${ATT}_{Damper} = {{- 2}0{\log_{l0}\left( {{10^{\frac{- {ATT}_{Combo}}{20}}} - {10^{\frac{- {ATT}_{{Full} - {block}}}{20}}}} \right)}}$

As shown in FIG. 6, the above-described prediction of an in-ear deviceattenuation filtered with acoustic dampers 48 is obtained from the anin-situ assessment of the acoustic seal performance of the device 12 andthe knowledge of the attenuation of the dampers 48 illustrated above.

For the filter selection, once the earplug 12 has been testedsuccessfully, an acoustical filter 46 can be placed into the inner bore20 (since the microphone probe has been removed) to let more sound getthrough. The filters 48 are, but not limited to, pure acoustical dampersthat are properly selected according to some guiding rules where theprotected exposure level is computed from the estimated attenuation ofthe passive earplug 12 and the time weighted exposure level of thesubject.

Such an acoustic protection test verifies what protection the earplug 12offers and allows to adapt this amount of protection to match the user'sneeds, in terms of providing the filtered predicted exposure level(F-PEL) of the individual with the earplug 12 when subjected to thespecific noise environment.

The present invention further refers to a method for assessing anacoustical performance of an in-ear device 12 using an apparatus 10, asshown in the simplified flow diagram of FIG. 7 in which all steps,including optional ones, are illustrated. The method comprises:

-   -   a) measuring a first sound level outside the ear canal 14 with        the sound measurement device 28 when submitted to the sound        source 24 and when located in a close relationship relative to        the in-ear device 12 and outside the ear canal 14;    -   b) measuring a second sound level inside the ear canal 14 with        the sound measurement device 28 when submitted to the sound        source 24 and when engaged into and occluding the passageway 20        with the in-ear device 12 inserted inside the ear canal 14 after        being fitted thereto and before removal therefrom;    -   c) measuring a third sound level inside the ear canal 14 with        the sound measurement device 28 when submitted to the sound        source 24 and when engaged into and occluding the passageway 20        with the in-ear device 12 inserted inside the ear canal 14 after        removal therefrom and reinsertion therein by the wearer thereof;    -   d) assessing a reference acoustic seal of the in-ear device 12        by subtracting the second sound level from the first sound level        and an actual acoustic seal of the in-ear device 12 by        subtracting the third sound level from the first sound level;        and    -   e) assessing a rating of the in-ear device 12 by comparing the        actual acoustic seal relative to the reference acoustic seal.

Step d) includes indicating presence of acceptable acoustic seal whenthe actual acoustic seal is within a predetermined range from thereference acoustic seal, for example within about 3 dB.

Step e) typically further includes comparing the obtained rating to astandardized rating value (NRR) corresponding to a type of the in-eardevice 12.

When using the dual microphone probe 26, steps a) and b) aresimultaneously performed using first 28 and second 30 sound measurementdevices, respectively. Then step c) includes measuring a third soundlevel inside the ear canal 14 with the second sound measurement device30 when submitted to the sound source 24 and when engaged into andoccluding the passageway 20 with the in-ear device 12 inserted insidethe ear canal 14 after removal therefrom and reinsertion therein by thewearer thereof, and measuring a fourth sound level outside the ear canal14 with the first measurement device 28 when submitted to the soundsource 24 and when located in a close relationship relative to thein-ear device 12 and outside the ear canal 12. The reference acousticseal of the in-ear device 12 is assessed by subtracting the second soundlevel from the first sound level, and the actual acoustic seal of thein-ear device 12 by subtracting the third sound level from the fourthsound level.

Typically, the method includes, before step a), the step of:

-   -   simultaneously measuring first and second reference sound levels        with the first and second sound measurement devices 28, 30,        respectively, when being submitted to a reference sound source        24 and when being in an acoustic near field relative thereto,        and determining a transfer function between the first and second        reference sound levels.

Then, assessment of the reference acoustic seal of the in-ear device 12is made by subtracting the second sound level from the first sound leveland using the compensation term (COMP) and the transfer function, andthe actual acoustic seal of the in-ear device 12 is made by subtractingthe third sound level from the fourth sound level and using thecompensation term and the transfer function.

A quick re-insertion test, corresponding to the post-curing sound levelmeasurements minus the subject-fit P-PAR measurements, is also performedby the present apparatus 10 in order to assess the quality of thereinsertion of an in-ear device 12 from objective measurements beforeremoval of the fitted device 12 and after re-insertion thereof by theuser himself.

The above rating test of the apparatus 10 ensures that the earplug 12offers at least the corresponding published NRR; thereby ensuring thatthe earplug 12 does not need to be derated (typically by a factor of twofor earplugs, according to Occupational Safety and Health Association(OSHA) to account for discrepancies between in-field performance andlaboratory certification measurement tests). For example, if the P-PAR(at 84% confidence level) is larger than the published NRR (about 17 dBfor example), then the user belongs to the 98% percentile category ofpeople having standard minimal required hearing protection and thereforenot subjected to any derating rule factor.

Alternatives

As shown in FIG. 1, a simple apparatus 10 of the present invention couldbe used to quickly perform on-site in-situ acoustic seal performancetest of in-ear devices 12 with simple handheld devices with simple userinterface 32 as controllers 22′ instead of more versatile computers 22that could allow to perform multiple different tests and measurementsfor different in-ear devices 12 with known normalized data storedtherein.

Although the present method and apparatus for objective assessment ofin-ear device acoustical performance have been described with a certaindegree of particularity, it is to be understood that the disclosure hasbeen made by way of example only and that the present invention is notlimited to the features of the embodiments described and illustratedherein, but includes all variations and modifications within the scopeand spirit of the invention as hereinafter claimed.

1. A method for assessing an acoustical performance of an in-ear deviceusing an apparatus having a sound measurement device connected thereto,the in-ear device having a passageway extending therethrough, thepassageway being in fluid communication with an ear canal of an ear whenthe in-ear device is inserted therein, the sound measurement devicebeing removably engageable into the passageway, said method comprising:a) measuring a first sound level outside the ear canal with said soundmeasurement device when submitted to the sound source and when locatedin a close relationship relative to the in-ear device and outside theear canal; b) measuring a second sound level inside the ear canal withsaid sound measurement device when submitted to the sound source andwhen engaged into and occluding the passageway with the in-ear deviceinserted inside the ear canal after being fitted thereto and beforeremoval therefrom; c) measuring a third sound level inside the ear canalwith said sound measurement device when submitted to the sound sourceand when engaged into and occluding the passageway with the in-eardevice inserted inside the ear canal after removal therefrom andreinsertion therein by the wearer thereof; d) assessing a referenceacoustic seal of the in-ear device by subtracting said second soundlevel from said first sound level and an actual acoustic seal of thein-ear device by subtracting said third sound level from said firstsound level; and e) assessing a rating of the in-ear device by comparingsaid actual acoustic seal relative to said reference acoustic seal. 2.The method of claim 1, wherein steps a) and b) are simultaneouslyperformed using first and second sound measurement devices,respectively.
 3. The method of claim 2, wherein step b) includes: b1)assessing validity of said first and second sound levels by determiningcoherence between said first and second sound levels, if not steps a)and b) are repeated.
 4. The method of claim 1, wherein step d) includesindicating presence of acceptable acoustic seal when said actualacoustic seal is within a predetermined range from said referenceacoustic seal.
 5. The method of claim 1, wherein step e) furtherincludes comparing said obtained rating to a standardized rating valuecorresponding to a type of the in-ear device.
 6. The method of claim 1,wherein step c) includes measuring a third sound level inside the earcanal with said sound measurement device when submitted to the soundsource and when engaged into and occluding the passageway with thein-ear device inserted inside the ear canal after removal therefrom andreinsertion therein by the wearer thereof, and measuring a fourth soundlevel outside the ear canal with said measurement device when submittedto the sound source and when located in a close relationship relative tothe in-ear device and outside the ear canal; and wherein step d)includes assessing a reference acoustic seal of the in-ear device bysubtracting said second sound level from said first sound level and anactual acoustic seal of thein-ear device by subtracting said third soundlevel from said fourth sound level, and wherein measurements of saidfirst and second sound levels are simultaneously performed using firstand second sound measurement devices, respectively; and whereinmeasurements of said third and fourth sound levels are simultaneouslyperformed using said second and first sound measurement devices,respectively.
 7. The method of claim 6, wherein step d) includesassessing a reference acoustic seal of the in-ear device by subtractingsaid second sound level from said first sound level and using acompensation term relating to the in-ear device, and an actual acousticseal of the in-ear device by subtracting said third sound level fromsaid fourth sound level and using said compensation term.
 8. The methodof claim 6, further including, before step a), the step of:simultaneously measuring first and second reference sound levels withsaid first and second sound measurement devices, respectively, whenbeing submitted to a reference sound source and when being in anacoustic near field relative thereto, and determining a transferfunction between said first and second reference sound levels.
 9. Anapparatus for assessing in-situ an acoustic seal of an in-ear device,the in-ear device having a passageway extending therethrough, thepassageway being in fluid communication with an ear canal of an ear whenthein-ear device is inserted therein, said apparatus comprising: acontroller unit operatively connectable to a sound source; a userinterface unit operatively connecting to said controller unit to allow auser to interface therewith by storing the predetermined acousticattenuation of the acoustic damper therein; and a sound measurementdevice operatively connecting to said controller unit, said soundmeasurement device being selectively locatable in a close relationshiprelative to the in-ear device and outside the ear canal for measuring afirst sound level outside the ear canal when submitted to the soundsource, said sound measurement device being removably engageable intothe passageway to selectively occlude the passageway for measuring, whensubmitted to the sound source, a second sound level inside the ear canalwith the in-ear device inserted therein being fitted thereto and beforeremoval therefrom, and a third sound level inside the ear canal thein-ear device inserted inside the ear canal after removal therefrom andreinsertion therein by the wearer thereof; said controller unitcalculating a reference acoustic seal of the in-ear device bysubtracting said second sound level from said first sound level, anactual acoustic seal of the in-ear device by subtracting said thirdsound level from said first sound level, and a rating of the in-eardevice by comparing said actual acoustic seal relative to said referenceacoustic seal.
 10. The apparatus of claim 9, wherein said controllerunit controls operation of the sound source.
 11. The apparatus of claim9, wherein said controller unit indicates presence of acceptableacoustic seal when said actual acoustic seal is within a predeterminedrange from said reference acoustic seal.
 12. The apparatus of claim 9,wherein said controller unit compares said obtained rating to astandardized rating value corresponding to a type of the in-ear deviceand stored therein.
 13. The apparatus of claim 9, wherein said soundmeasurement device is a first sound measurement device, said apparatusfurther including a second sound measurement device operativelyconnecting to said controller device, said first sound measurementdevice being selectively locatable in a close relationship relative tothe in-ear device and outside the ear canal for measuring the first anda fourth sound levels outside the ear canal when submitted to the soundsource, said second sound measurement device being removably engageableinto the passageway to selectively occlude the passageway for measuringthe second and third sound level inside the ear canal with the in-eardevice inserted therein when submitted to the sound source; saidcontroller unit assessing a reference acoustic seal of the in-ear deviceby subtracting said second sound level from said first sound level andan actual acoustic seal of the in-ear device by subtracting said thirdsound level from said fourth sound level.
 14. The apparatus of claim 13,wherein said first and second sound measurement devices are connected toone another.
 15. The apparatus of claim 14, wherein said first andsecond sound measurement devices are connected in a back-to-backrelationship relative to one another.
 16. The apparatus of claim 14,wherein said first and second sound measurement devices form a dualmicrophone probe.
 17. The apparatus of claim 16, wherein said controllerunit assesses validity of said first and second sound levels bydetermining coherence between said first and second sound levels, if notsaid first and second sound levels are being re-measured.
 18. Theapparatus of claim 17, wherein said controller unit assesses validity ofsaid third and fourth sound levels by determining coherence between saidthird and fourth sound levels, if not said third and fourth sound levelsare being re-measured.
 19. The apparatus of claim 18, wherein saidcontroller unit determines coherence between said first and second soundlevels within a predetermined frequency range and between said third andfourth sound levels within said predetermined frequency range,respectively.